1. Field of the Invention
The present invention pertains to an apparatus and a program for update of a time stamp to be able to certify certification target data on the basis of time stamp data transmitted from an apparatus for time stamp authority.
2. Description of the Related Art
A request for forensic technology has increased as development of an information processing apparatus in recent year. The forensic declares a series of a scientific search method and technology which performs preservation of evidence and research/analysis of an electromagnetic record, and performs analysis/data gathering, etc. such as the falsification and damage of the electromagnetic record, to an incident response and legal dispute/lawsuits. Here, the incident response declares response to unauthorized use of resources and environments on a computer and a network, etc., service sabotage, destruction of data, disclosure of information not intended etc., and action (incident) etc. to arrive at them etc. According to such the forensic technology, computer security can be maintained to positive by secure of the digital evidence being attempted.
As one of the technologies of this forensic, a digital signature and a time stamp are proposed. According to the digital signature, an author and contents of electronic data are able to specify. On the other hand, according to the time stamp, the existence time of the electronic data is able to certify. More specifically, the time stamp has improved probative force of the electronic data by each certificate function of existence certification and integrity certification. The existence certification certifies when the electronic data exists until. The integrity certification certifies whether or not the contents of the electronic data are falsified.
The time stamp is certified by a certificate issued by an apparatus for time stamp authority of Time Stamp Authority (TSA) with the authority of RFC3161 and ISO18014. For example, when hash value obtained from the electronic data to be certified by a hash function is transmitted to the apparatus for time stamp authority, generates information on the time certificate etc. in the apparatus for time stamp authority on the basis of the received hash value and it replies. When verifying, the hash value is calculated on the basis of the verification target data, and the calculated hash value and the hash value included in the time certificate are compared. As a result, if both are matched, it is certified that the verification target data exists at the time and is not falsified.
In general, there is a method of automatically performing an extension operation of the validity period of the digital signature (for example, Japanese patent Laid Open Publication (Kokai) No. 2002-6739). According to this method, the throughput of the re-signature of the digital signature can be reduced.
Moreover, as a method of certificating the time stamp during the long-run, a method that certifies by valid time stamp for a long term and a method that certifies for a long term by extending the validity period for a short term repeatedly of the valid time stamp etc. are disclosed (for example, “GUIDELINE OF TIME STAMP FOR LONG-RUN CERTIFICATION”, February 2005, Time Business Forum (TBF), “URL:http://www.scat.or.jp/time/PDF/choukihosyouguidelin eVer1.1.pdf” searched on Jul. 15, 2005).
However, according to the method of the latter mentioned above, there is a problem that the certification at the time certified by the time stamp becomes impossible when one time stamp is invalid. At this time, even if the certification target data is not falsified, there is a possibility that the existence certification at the predetermined time becomes impossible by incompletely and leaking of the time stamp.
Then, the method of surely enabling the existence certification of the certification target data for a long period has been expected.